How do we measure distances on cosmic scales? This lecture describes

the rungs in the cosmic distance ladder from measuring the AU in our

own Solar System out into the Hubble expansion of the universe. These

distances form the basis of the measurements that let us piece together

the present, past, and future history of the expanding Universe, setting

the stage for next week's lectures.

Recorded 2006 February 24 in 1008 Evans Laboratory on the Columbus campus

of The Ohio State University.